To a mixture consisting of 1.5 g (7.5 mmol) of the ketone derivative, i.e., (3-propionyl-5-phenylisoxazole) prepared above in the procedure (3), 0.99 g (8.2 mmol) of piperidine hydrochloride, 0.36 g of paraformaldehyde and 3 ml of dioxane, 0.03 ml of 12N-hydrochloric acid was added. The resultant mixture was heated under reflux for 2 hours. After completion of the reaction, ethyl ether was added. Colorless crystals thus formed were collected by filtration and added to a saturated aqueous solution of sodium hydrogencarbonate. The solution was extracted with ethyl ether. The solvent was distilled off so that 3-(2-methyl-3-piperidinopropionyl)-5-phenylisoxazole was obtained as colorless crystals.
